Fire alarm switch



July 21, 1953 1. F. PYLES 2,646,480

FIRE ALARM SWITCH Filed Aug. 29, 1950 2 Sheets-Sheet 1 Fig.

Fig'z Fig.3

Ira F. Py/es INVENTOR.

BY Mm.

July 21, 1953 1" F. PYLES 2,646,480

FIRE ALARM SWITCH Filed Aug. 29, 1950 2 Sheet -Sheet 2 INVENTOR.

mlyww 5m Patented July 21, 1953 UNITED stares rarest or ies FIRE ALARM SWITCH Ira F. Pyles, Fairviemllb Application August 29, 1950, Serial No. 182,080

main object to provide a simple and inexpensive switching and sounding apparatus which is foolproof and which is protected against all extraneous sources of disturbance and which may be mounted or installed anywhere and which will operate with all types of current.

A further object of the invention consists in providing a temperature sensitive sound alarm system which is operable by a thermic switch element preferably of the bimetallic type and which permits the use of any number switches in series with the alarm device, the latter producing sounds materially different from those produced by the customary alarm bell which are, therefore, easily distinguishable.

A further object of the invention consists in providing an automatic fire alarm system with bimetallic thermic units which, while protected against external mechanical influences, are so shaped that their formation produces considerable contact pressure and contact on relatively large area.

Further and more specific objects of the invention will be apparent from the following detailed specification.

The invention is described with reference to the accompanying drawings illustrating two embodiments thereof. It is, however, to be understood that the embodiments illustrated in the drawings areshown by Way of example only and for the purpose of explaining the principle of the invention and the best mode of applying the principle. Further modifications will be obvious to the experts skilled in this art and a departure from the modifications shown in the drawings is, therefore, not necessarily a departure from the essence of the invention.

In the accompanying drawings:

Figure 1 is a diagram illustrating the use of 'thermic elements in connection with alarm devices of the customary type;

Figure 2 is an elevational cross section through one of the thermal responsive elements;

Figure 3 is a fragmentary elevational and sec tional view similar to the view shown in Figure 2, the section being however taken along the line 33 of Figure 2;

Figure 4 is a diagrammatic partly sectional View of the thermal responsive elements and of the alarm device, all the views being partly sectional;

of thermic 1 Claim. ((31. 200-138) iii Figure 5 is a partly sectional front View of the alarm device, the section being taken along the line 5-5 of Figure 4;

Figure 6 is aplan view of the thermostatic element;

Figure '7 is a cross-sectional view through the bi-metallic strip with its contacts and also through the stationary contact with which the strip cooperates, the section being taken along the line l''l of Figure 6.

In the embodiment of the invention according to Figures 1, 2 and 8, a base member i t of'frustoconical shape is provided which may be mounted on the wall or on the ceiling or on a, horizontal board, ledge or shelf, and which carries the thermic element. Near the base of the frustoconicalelement cuts may be provided for the introduction of the wires leading to the contact controlled by the thermic element. The top of the frusto-conical base member is covered with a base sheet l2 which is preferably encircled by a short cylindrical upstanding flange orcollar i5.

The base sheet l2 carries an insulating plate H which is fixed to said base sheet by means of terminal posts 20, 2| surrounded by insulating flanged sleeves i9. These posts 20 and 2% also form the terminal posts for the two contact carrying members it which may consist of two short angle pieces one flange of which is held on the insulating plate ll while the other flange is projecting at right angles thereto. The tips of the two angles It carry the contact buttons it.

It will be understood that on account of the mounting of the contact carrier on the insulating plate the two contacts are normally insulated from each other.

Either on the base sheet I2 or preferably on the cylindrical flange it the bimetallic thermic elementtt is mounted by means of an insulated washer 22 and by means of rivets. This element is U-shaped, one leg 29 being longer and fixed to the flange i5 as above described, while the other element which is parallel thereto is shorter as shown at 28 and carries at its end an insulating longitudinal strip 24 which fixed to the bimetallic strip by means of rivets or bolts. This insulating strip in its turn carries a transverse bridging contact member 25 which faces the contact buttons is and is adapted to be brought into operative contact with said buttons. The two legs 28 and 29 are joined b a sharp bend 2? the stretching of which under the influence of heat moves the shorter leg 25 towards the two contacts 16. On account of the sharp curvature which may be selected in a suitable manner the transverse member is applied against the contacts under considerable pressure which increases with the temperature to which the element is subjected. Under such pressure good contact is made even if the contact buttons IE or the transverse contact bridge member 25 are no longer in a freshly polished condition.

A wire meshing 26 forming a closed cylinder with a closed dome-shaped top surrounds the thermic element and the contacts completely and protects these elements against mechanical influences and especially against accidental contact between the members l6 and 25 due to introduction of extraneous objects which may press against the thermic elements or which may accidentally penetrate into the space between the contacts 25 and [6.

Any number of thermic elements, generally 1-1 designated by the reference numeral 8 in Figures 1 and 4 may be connected in parallel with alarm circuit 9. The alarm circuit may be branched oil from any junction box 32 connected with the supply wires of a building. An ordinary alarm device 33 may be used in connection with the thermic switches and in this case is inserted into one of the branches of the alarm circuit 9. If a plurality of thermic elements is used they are all connected in parallel with the branches of the alarm circuit.

In Figures 4 to 7, a slightly diiierent type of thermic element 8 and also a different alarm sounding device is shown.

The bimetallic strip is mounted within an open box 39, preferably of insulating material through which air may freely circulate. The metallic element is thus exposed to the temperature of the air. The box 39 carries the post or pillar '22 on which the bimetallic strip 30 is mounted. The said strip in this case may be rectilinear and carries on its end a contact element 15 of a triangular cross section, Figures l and 7, which is attached to said strip. This wedge-shaped element is adapted to be pressed into the space between the two flaring contacts 68 and '57 which are mounted in the insulated box by means of rivets or bolts 53, 46 which also serve as terminal posts for the connection of the contacts 40, 4'! with the branches of the alarm circuit. Obviously, when the bimetallic strip is flexed, the wedge-shaped bridge element is pressed in between the flaring ends of contact members 4 5 and 4? under considerable pressure at higher temperatures. The two contacts 46 and 37 are thus bridged by the contact member 45 and, therefore, a connection is made between the two branches 9 and 9" of the alarm circuit 9.

While the wedge-shaped bridge contact member 45 may be placed transversely with respect to the bimetallic strip as shown in Figures 6 and 7, the said element may also be placed longitudinally.

The two branches 9' and 9 may be connected with one of the outlets of the network of the building.

One of the branches includes the alarm apparatus which in this case consists of a small electric motor 48 driving a shaft 49 on which is seated, by means of a sleeve 51 and a set screw 52, a disk 50. This disk rotates within the body of a bell 55, carried by means Of bolts and spacers 5'! on a bail 58 which is fixed to the casing of the motor 48. As shown, the disk may rotate within the bell 55. The disk is provided with bolts 54 forming pivots and striker arms 56 which may swing around the bolts 54 and which may also be permitted some longitudinal movements by providing elongated bores through which the pivots 54 may pass on said striker arms.

A striker pin 50 may be arranged within the bell and may be attached to the bottom of the said bell. When, therefore, the motor starts to rotate the striker arms 55 assume a radial position and during rotation therefor will strike against the pin 50 and will thus produce, on account of the high frequency with which the pin is struck, a peculiar kind of sound which is distinguished from an ordinary sound produced by the customary alarm bell.

Obviously, also in the arrangement according to Figure 4, any number of thermic elements may be connected with the alarm circuit 9 in the manner shown in said figure, two elements being shown in order to illustrate said connection.

The operation of the system will be clear from In the event or" flames box 39 or in the event of such flames heating the surrounding the wire or passing through the box 39 the thermic element will operate and will produce a contact between the two con act buttons or flaring contacts, thus closing the alarm circuit a. The alarm sounding device series with one of the branches of the alarm circuit is then operated and produces a sound in the manner already indicated.

It will be clear that all essential details may be changed without in any way departing fromv the invention as defined in the annexed claim.

Iiaving described the invention, what is claimed as new is:

An alarm device comprising an elongated casing with parallel walls, an elongated substantially flat bimetallic strip arranged i substantial parallelism to the wall of the casing, a fixed support for said strip near one end of the casing, the other end. being free and near the other end of the casing, a wedge shaped prismatic bridge contact of substantially triangular cross section carried by said bimetallic strip and fastened with its base at right angles to the bimetallic strip, the edge of the wedge runnin in substantial parallelism to the flat bimetallic strip, two elastic upstanding alarm circuit contacts insulated from each other and mounted. on said insulating casing at a distance from each other on a wall of the casing parallel to and facing the bimetallic strip, contact surfaces arranged at the ends of the clastic upstanding alarm contact substantially parallel to the wedge surfaces, said alarm circuit contacts being placed close to each other, the contact surfaces of both alarm circuit contacts forming a wedge like structure having substantially the same cross section as the wedge shaped contact carried Ly the bimetallic strip, the latter when bent by unequal dilation pressing the wedge shaped prismatic contact into the wedge formed by the contact surfaces of the alarm circuit contacts.

IRA F. PYLES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 648,432 Prentiss May 1, 1900 928,934 Brent July 27, 1909 1,822,472 Brady Sept. 8, 1931 1,972,975 Brady Sept. 11, 1984 2,217,551 Herman et al Oct. 8, 1940 

